1. Field of the Invention
The present invention relates to an acetabular cup navigation system for calculating an insertion direction of an acetabular cup inserted into the pelvis for total hip replacement surgery, and more particularly, to a T-shaped gauge and acetabular cup navigation system and acetabular cup aligning method using the T-shaped gauge for exactly calculating an insertion direction of an acetabular cup, which will be inserted into the pelvis, by measuring anatomical landmarks of the pelvis at once and measuring pelvis coordinates changed during surgery in real time.
2. Background of the Related Art
In a conventional artificial joint surgery for replacing hip joints with artificial joints, the artificial joints could not be inserted into the hip joints in an exact orientation (or angle) because the orientation (or angle) of the the artificial joints inserted into the hip joints is defined by a doctor's experiences and a mechanical gauge provided by an artificial joint manufacturer. Furthermore, as patients' pelvis sizes and shapes are different according to the patents' body conditions, the artificial joints cannot be inserted into the hip joints in the exact orientation (or angle). If the artificial joints are inserted into the hip joints in a deviated orientation from the normal orientation, the patent who undergoes artificial joint surgery has to experience surgery again so that the artificial joints are located at an exact orientation of the hip joints.
Therefore, to address the above problem, a navigation system for surgery of hip joints is induced so that the doctor can obtain information of alignment of artificial joints inserted into the hip joints in real time during the surgery. The navigation system is used to match the artificial joints to the patient's pelvis based on three-dimensional image of the patient's pelvis part obtained through a CT scan. For example, for total hip replacement surgery, the navigation system is used to determine a orientation of an acetabular cup inserted into the acetabulum of the pelvis based on an anterior pelvic plane formed by three points, which are called as anterior superior iliac spines and pubis part.
In order to operate the artificial joints using the conventional navigation system, there is a need for a registration of making a transformation matrix of the exact position of the pelvis for the surgery of the artificial joints using image information of the patient's pelvis obtained by the CT scan. To carry out the above process, a fiducial marker is inserted into the patient's pelvis before surgery to measure the corresponding position, or points of several tens are measured at the pelvis part of a cut part during the surgery. Moreover, the CT scan may have an adverse influence on the patient's health and is very expensive as using radial rays at a corresponding region of the patient's body to be operated surgically to obtain the three-dimensional image.
Meanwhile, to solve the disadvantages of the CT scan, directly before the surgery of the artificial joints, using a measuring device, the three anatomical landmarks of the pelvis are measured on the skin corresponding to the patient's pelvis position, and then, the surgery of the artificial joints is performed based on the three anatomical landmarks.
However, as the measuring device measures the three anatomical landmarks respectively, the measured anatomical landmarks have a relatively measuring deviation by the hypodermic fat. Therefore, the artificial joint surgery using the measuring device may considerably deteriorate accuracy to exactly insert the acetabular cup into the acetabulum, and the patient who has been operated has to be operated again to correct the orientation of the artificial joints.